At least seven people have been killed and dozens injured in a suicide bombing during Mass at a Catholic church in northern Nigeria, officials say.
An explosive-laden vehicle drove into the church and detonated its load, ripping a hole in the wall and roof.
The attack happened in Kaduna, which has been targeted by Islamist militant group Boko Haram in the recent past.
President Goodluck Jonathan promised to "redouble" his government's efforts to tackle terrorism and violence.
He called the attack part of an "unfortunate and unacceptable trend that threatens the peace and stability of our nation".
A spokesman for the local governor has called for calm, pleading with people on local radio not to retaliate.
The Nigerian Emergency Management Agency told the BBC that Christian youths attacked a vehicle that had come to rescue survivors after the attack, smashing one of the windows.
Unconfirmed reports said at least two people were killed in reprisal attacks by Christians after the bombing.
No group has said it carried out the bombing.
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